This invention relates to a composition and to methods of creating a polymeric material or substrate (as defined hereinafter), preferably in the form of a formed plastic product, thin layer film, laminate, or a composite with a solvent-borne antimicrobial agent in order to eliminate microbial growth on or in the material or substrate.
More particularly, this invention relates to a novel way to form an antimicrobial homopolymer or copolymer with a polymeric substrate, such that it has a non-leaching antimicrobial property that is not dependent on leaching antimicrobial agents. The methods described herein may be used to prepare or treat biocompatible devices or other products and impart antimicrobial properties to polymeric substrates containing the antimicrobial agent throughout the polymeric substrate.
There has been a great deal of attention in recent years given to the hazards of bacterial contamination from potential everyday exposure. Noteworthy examples of such concerns include the fatal consequences of food poisoning due to certain strains of Eschericia coli being found within undercooked beef in fast food restaurants; Salmonella contamination causing sicknesses from undercooked and unwashed poultry food products; and illnesses and skin infections attributed to Staphylococcus aureus, Klebsiella pneumoniae, yeast, and other unicellular organisms. With such an increased consumer interest in this area, manufacturers have begun introducing antimicrobial agents within various everyday products and articles. For instance, certain brands of polypropylene cutting boards, liquid soaps, etc., all contain antimicrobial compounds. The most popular antimicrobial agent for such articles is triclosan. Although the incorporation of such a compound within liquid or certain polymeric media has been relatively simple, other substrates, including thin polyurethane films, have proven less accessible. Such compounds are highly desired for films to provide not only antimicrobial benefits, but also to control mildew and odors. In particular, such films are highly desired for utilization as fabric coatings, food preserving articles such as food containers and wrapping materials, both to prevent introduction of pathogens within the protected food items (i.e., meat, for example), as well as to destroy any bacteria or other pathogenic microorganisms retained within the food package prior to and possibly during storage, and the like.
As used herein, an “antimicrobial agent” is an agent that destroys or inhibits the growth of microorganisms, and particularly pathogenic microorganisms. The major classes of microorganisms are bacteria, fungi including mold and mildew, yeasts, and algae. Microorganisms can be found in the air, the water, in and on the human body and bodies of animals, soil, wastes, and on all surfaces. The microorganisms are deposited from the air, food and drink spills, dust, dirt and tracked in soil, and from human and animal excreta such as sweat, urine, and feces. Organisms grow and multiply when there is available a nutrient source of food such as organic or inorganic material contained in such wastes, dirt, dust, and living tissue. For growth and multiplication, most microorganisms also require warm temperatures, and moisture. When these conditions exist, microorganisms multiply, grow and flourish. Microbial growth, however, leads to many problems, such as unpleasant odors ranging from stale to musty and mildew-like, to putrid and foul smelling, resembling ammonia. The growths also produce unsightly stains, discoloration, and deterioration of many surfaces and materials in which they come into contact. A more serious disadvantage of microbial growth is the proliferation of pathogenic microorganisms, their metabolic products and their somatic and reproductive cell parts, which contribute to the spread of disease, infection, and health disorders.
Although triclosan and other organic compounds have been taught for such purposes, due to migration concerns and potential health issues with such organic based compounds and compositions, such antimicrobial agents are now avoided, particularly when in potential contact with human skin or items for human consumption.
Discoloration of the films themselves is to be avoided in order to provide a relatively clear storage article. Yellowing or browning is highly discouraged in this sense. The utilization of silver-containing compounds in the past has presented certain potential problems with discoloration, such that improvements in this area are highly desired as well.
Silicon-containing quaternary ammonium salts having the following Formula I are recognized antimicrobial agents:R3N+R0nSiX4-nY−  (I)wherein each R and each R0 is independently, a non-hydrolysable organic group; each X is, independently, a hydrolysable group; n is an integer of 1 to 3; and Y is a suitable anionic moiety to form the salt of the compound of Formula I.
The use of such silicon-containing quaternary ammonium salts in solvents adsorbed by a polymeric substrate surface where the quaternary salt is subsequently polymerized such that an interpenetrating network is formed within the interstices only of the polymeric substrate surface has been described in U.S. Pat. Nos. 6,146,688 and 6,572,926, the disclosures of which are hereby incorporated herein by reference.
Despite knowledge of the common usage of silicon-containing quaternary ammonium salts for imparting antimicrobial properties to surfaces, a method was not known for protecting surfaces through the use of antimicrobial agents polymerized throughout the entire substrate including throughout the bulk material used to make the substrate or throughout the thin layer film or laminate. The benefit of such a process and the products produced thereby is that antimicrobial protection is still available even if the surface is abraded or removed during the manufacture or use of a substrate or thin layer film or laminate. This is accomplished with the present invention.
The use of such silicon-containing quaternary ammonium compounds as antimicrobial agents in accordance with the prior art is well known and taught in a wide variety of U.S. patents, e.g., U.S. Pat. Nos. 3,560,385; 3,794,736; 3,814,739; 5,954,869; the disclosures of which are hereby incorporated herein by reference. It is also taught that these compounds possess certain antimicrobial properties, which make them valuable and very useful for a variety of surfaces, substrates, instruments and applications (see, e.g., U.S. Pat. Nos. 3,730,701; 3,794,736; 3,860,709; 4,282,366; 4,394,378; 4,408,996; 4,414,268; 4,504,541; 4,615,937; 4,620,878; 4,631,273; 4,692,374; 4,842,766; 5,064,613; 5,358,688; 5,359,104; 5,411,585; 5,954,869; 5,959,014; 6,113,815; 6,120,587; 6,221,944; 6,469,120; 6,632,805; and 6,762,172; the disclosures of which are hereby incorporated herein by reference).
These silicon-containing quaternary ammonium antimicrobial compounds are available and widely used as disinfectants and biocides and to treat items that may undesirably support microbial growth. For example, silicon-containing quaternary ammonium salts are used to treat carpeting, walls, various commercial products such as sponges and fabrics, and even water. They are also used to rehabilitate “sick buildings,” particularly after floods and water leaks, and reduce odors caused by mildew, fungi and bacterial growth in damp basement areas.
Most silicon-containing quaternary ammonium salts commercially available are generally pre-packaged in water or alcohol solutions of approximately 2-3 weight % or less quaternary salt concentration. They are applied to substrate surfaces, such as carpets, walls and floors, to kill the bacteria. The method of application often relies on delivering the silicon-containing quaternary ammonium salt in a fine spray. When treating fabrics, sponges, bedding, and similar products, the concentration of the quaternary ammonium salt generally can be much lower, e.g., less than 1 weight %.
More specifically, because hospital-acquired infections are the leading cause of hospital or long-term care infections, numerous attempts have been made to create antimicrobial surfaces in hospital and medical facilities. Most treatments rely on the use of antimicrobial washes to achieve a coated surface that is resistant to bacterial growth. Unfortunately, this indiscriminate use of antimicrobial agents results in the build up of increased resistance of bacteria and certain other microorganisms to the widely used antimicrobial agents. This presents a significant problem for those being treated in health care facilities, and particularly for immune-compromised patients.
Further, some antimicrobial surface treatments use a coating treatment that provides a vehicle for entrapping the antimicrobial agent on the surface but permit subsequent diffusion of the antimicrobial agent into the biological environment. Many such treatments rely upon a leaching mechanism to deliver the antimicrobial agent into the environment.
Thus, a method has not been devised to impart non-leaching, biocompatible, antimicrobial properties through out the entire substrate, thin film layer or laminate. Only the very surface has previously been made antimicrobial with a non-leaching antimicrobial agent through the formation of an interpenetrating network at the interface of the substrate surface and the antimicrobial agent, for only as deep into the surface as the antimicrobial agent could be adsorbed into the substrate. The present invention of making a homopolymer or copolymer of a silicon-containing quaternary ammonium salt of Formula I within a polymeric substrate, preferably in the form of a thin layer film or laminate, provides added benefits of sustained antimicrobial properties.
There has been a long-felt need to provide durable, reliable, long-lasting, non-leaching antimicrobial substrates, especially in the form of thin layer films and laminates, formed plastic products and composite materials that exhibit effective sustained antimicrobial characteristics throughout the substrate. Unfortunately, to date, no such substrates or materials were available that contained a non-leaching antimicrobial agent. The present invention satisfies this long-felt need.
Among other things, the present invention relates to a method for creating an antimicrobial agent for manufacture of medical devices and supplies that is biocompatible and antimicrobial throughout the entire composition of the device or supply.
The present invention also relates to a method for creating a biocompatible and antimicrobial material for use as or with building materials, paint thin films and consumer products.
The present invention further relates to an antimicrobial laminate counter top that is not dependent on leaching antimicrobial agents for surface microbial protection.
The present invention additionally provides a method for creating a copolymeric thin layer film or laminate having antimicrobial properties that can be applied to various medical and food supply surfaces.